Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Yesterday's drop in the stock market turned into a rout Friday, as investors added fears of an emerging-market currency crisis to previous concerns about international economic growth. Despite some bullish earnings reports from key large-cap stocks, major-market indexes dropped 2%. Yet, for Texas Industries (UNKNOWN:TXI.DL), Open Text (NASDAQ:OTEX), and VelocityShares Daily 2x VIX ST ETN (NASDAQ:TVIX), the down day didn't prevent their shareholders from seeing big gains.

Texas Industries jumped 9% after reports surfaced that the building materials company might be a takeover target, with construction-aggregates peer Martin Marietta Materials (NYSE:MLM) seen as the potential buyer. The move would make sense by giving Martin Marietta a bigger presence in the key Texas and California construction markets. With Texas Industries having cement-making capacity, the combination could prove well-timed as conditions in the U.S. construction industry start to improve. Two major investors in Texas Industries have been looking at strategic options to divest their interests for a while; therefore, a buyout could be good for everyone involved.

Open Text climbed nearly 11% after the enterprise-software company reported earnings last night. Open Text beat expectations on both revenue and earnings, reporting a 7% jump in licensing revenue, and a 6% rise in its customer-support division. Open Text also said it would split its shares two-for-one, a move that has become increasingly rare among stocks in recent years.

The VelocityShares leveraged volatility exchange-traded note soared 17% on a big spike in the S&P Volatility Index (VOLATILITYINDICES:^VIX), which itself posted a 31% gain to its highest levels since October's U.S. government shutdown. Many investors might be confused about why the leveraged ETN didn't rise further, but the key to remember is that the VelocityShares offering tracks futures contracts on the Volatility Index rather than the spot index figure itself. Nevertheless, the gain represents only a small move up for the ETN, which lost about 85% of its value in 2013 amid a year with almost no volatility.